


Seeing the Stars

by SheeWolf85



Category: Undertale (Video Game)
Genre: College AU, College Student Reader, Cunnilingus, DFAB reader, Desk Sex, Ectobiology, F/M, Fellatio, Female Reader, Sexy Times, Smut, Tumblr request, adult reader, professor sans, professor/student, sans/reader - Freeform, who can blame you tho really, you fuck your professor, you got the hots for your professor, you suck the dick
Language: English
Status: Completed
Published: 2018-11-18
Updated: 2018-11-18
Packaged: 2019-08-25 04:15:32
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,393
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16654072
Author URL: https://archiveofourown.org/users/SheeWolf85/pseuds/SheeWolf85
Summary: You are a college student who's got the hots for your astronomy professor, Sans. It's all one-sided, of course--or so you think. One day you get a call from Professor Sans about a paper you wrote and learn that you really need to edit your papers better before turning them in.  That's okay, Sans is into it.





	Seeing the Stars

**Author's Note:**

> Written for an anonymous request on Tumblr asking for Professor Sans with college student Reader sexy times. They had some specific scene ideas that I really enjoyed, and I hope I did them justice. 
> 
> Thank you so much for sending this in! I had so much fun writing this, even if it did take me for-fucking-ever to finish it! I hope you see this and enjoy it!

You’d taken the class because it was supposed to be a quick and easy way to get a good grade and credits toward your degree. Your pursuit of a business degree didn’t have much to do with astronomy in the least, but you were at least interested in the subject.

When you learned that the class was being taught by a monster, you weren’t bothered even a little. You’d already had a few classes taught by monsters and found that their enthusiasm for their subjects made them some of the best professors you’d ever had. What you didn’t expect was for this particular professor to be so damn…amazing.

In every sense of the word.

Except maybe his fashion sense, because that was a little weird. The guy wore pink, fluffy slippers with black basketball shorts and a blue hoodie to class. Occasionally, he’d wear flip-flops with socks. You were pretty sure he did it just to annoy the other professors who took pride in wearing suits to teach their classes.

You’d excelled in his Intro to Astronomy class for a few reasons, and you’d be lying out your ass if you said one of them wasn’t because you wanted to impress him. Professor Sans was a skeleton monster, maybe a little short-statured for a monster but still a bit taller than you. His voice was deep and gruff and so captivating you had no trouble hanging on every word he said. It wasn’t two weeks into his class when you realized you were beginning to harbor a little crush on him. You’d made up issues with assignments for the sole reason of finding him during his office hours and talking with him one on one.

As busy as he was, he never once told you to figure it out on your own. He’d take the time you needed to explain something to the point that a kindergartner could get it. After the first few times, you decided to stop doing that because you didn’t want him to think you were stupid. And, honestly, you were pretty sure he was catching on to your antics when he said to your face that he knew you were smarter than you were letting on. He also said he didn’t mind you coming in to just talk to him. He didn’t have a lot of friends, and while being your professor meant he couldn’t really be your friend, he liked meeting people who obviously liked astronomy at least half as much as he did.

A few times during your chats with the professor, you thought you’d catch him staring at you. It was probably your imagination—wishful thinking. Was it also your imagination when you’d hand in papers and he’d give you that grin with a wink and his phalanges would purposefully linger on your fingers? Probably.

And so you’d made the decision to take a more advanced astronomy class the next semester. A tiny part of you wanted to change your major simply so you’d have a valid excuse to keep taking his classes.  It only got more tempting as the second semester went on.

Just after mid-semester, you got a call from Professor Sans. He wanted you to come in and speak with him about the paper you’d turned in.

You were a little nervous; you had worked your ass off on that paper, and it had been the hardest assignment you’d had to date. You had to write about celestial bodies and how their relative gravity fields would affect other bodies around them. You had barely finished the assignment on time, taking a few breaks throughout to fantasize about your professor in ways you would never admit to out loud. The crush you’d developed during your first class with him had morphed into wet dreams and nightly masturbation to the thought of his voice and his hands touching you and…yeah, you were already getting hot again. Damn.

A part of you wanted to try to dress up cute for your meeting with him.  Then again, you were pretty sure he was going to tell you that you’d failed the assignment. Just because you had something of a friendship with him didn’t mean he could give you a second chance to rewrite your paper. Instead of dressing up, you put on a pair of dark blue leggings and a large, comfortable sweatshirt.

Professor Sans’ office was always at a level of organized chaos that you would never understand. Books and papers were strewn around, stacked on top of every available surface, some even on the floor. He also taught physics (imagine your surprise—or lack thereof—when you realized he also taught astrophysics) and robotics. He was a genius, so it was okay that he was his own brand of disorganized.

He wasn’t in his office when you stepped inside. You took a moment to look around as you made your way to his desk. To your amazement, it was clean. You had never once seen Sans’ desk clear of clutter. He always had a few books or trinkets he was working on or some experiment or another on his desk. Today, he did not. The sight of it actually worried you a little.

Instead of dwelling too much on the weirdness, you sat down in the chair and looked around. He had a few photos in frames by his computer. One was of him and a taller skeleton he’d told you was his brother. Papyrus taught physical education at a nearby high school and also offered self-defense classes for monster and human children. Another photo was a wedding between a scary-looking fish lady and a lizard monster. Both were smiling and obviously so happy.

“glad you could make it.”

Sans’ deep voice behind you made you jump. You turned to look at him, not surprised in the least to see him dressed in a white t-shirt and black shorts, those damn sandals with socks on his feet. One of his hands was tucked into his shorts pocket while the other held what you assumed to be your paper.

He shut his office door—not an uncommon thing for him to do during your talks—and made his way around the desk and sat down, putting the paper face-down in front of him. “how goes it?”

You shrugged. “It goes okay, I guess.”

This was good; the few times he’d had to talk to you about your assignments always started out with small talk. The one and only time you’d actually failed an assignment, he’d gotten right to the point and asked you how he could help you.

He nodded and leaned back in his chair. This time you were one hundred percent sure he was staring at you. Not just staring, either; he was watching you with something you could only describe as predatory in his white eye lights. His hands folded together in front of him, and he just watched you.

Only a few seconds ticked by before he cleared his throat and sat up straight. “how are you liking your classes this semester? everything going okay?”

You swallowed, a little unsure of what exactly was going on. You sure as hell didn’t mind him looking at you the way he was, but you were pretty damn certain you’d have to find somewhere private before you got home to take care of a little business. The way he stared went straight between your legs.

“Um, yeah. It’s been a good semester.” You nodded. Your palms began sweating a little as he leaned forward even more, setting his still-folded hands on the desk in front of him.

“good. anything i can do to help you out?”

Your heart began thumping so hard in your chest you were certain he could hear it. Goddamn, the way he said those words made it sound like he was asking to fuck you.  You knew without a doubt that wasn’t the case. He was merely a concerned professor; someone you really hoped could be an actual friend once you were finished with his classes.

“I don’t think so. Um, did I do something wrong? On my paper?” You needed to get this conversation over with so you could go cool off a little. You had class with him later that evening, and you really needed to be able to focus on more than how his voice made your body want an orgasm.

He blinked once. Twice. Then he chuckled. Goddamn that chuckle. His laugh was deep and soft and went through your whole body.

“nah, not really. you did good research and obviously paid attention in class.  but hey, did you proofread your work?”

He did it again. That stare was positively rapacious, like he was desperate for something he knew he couldn’t have. You sure as fuck knew the feeling.

You licked your lips and shifted in your seat, trying to convince your body to calm down because you were not going to fuck your professor any time soon.

“Yeah, of course I did.”  You had spent all damn night on that godforsaken paper.

He nodded, then turned the assignment still in front of him over. He flipped through the pages; thirteen in total. It was technically supposed to be fifteen, but you had never been a very good writer and he’d already given you and several other students a little leeway in that department. His eye lights scanned through the second-to-last page, and you noticed the moment he caught whatever it was he wanted to talk to you about. His body tensed, and his eyes darted to you in a flash before going back to the paper.

Well, fuck.

He then handed the paper to you.  “read the third paragraph.”

You took the paper, your mouth going dry as you scanned the paper.

“out loud,” he added when you began to read silently.

You cleared your throat and began reading.  You really had done your research. Everything sounded fine.

Until about four sentences in. Your eyes caught the line before you’d made it that far verbally.  There, in the middle of your assignment, were the words, “goddammit Sans just fuck me.”

You stopped reading the moment you saw those words. Your whole body went numb. How fucking stupid could you get? You remembered now writing out a whole scene prior to masturbating to a fantasy of Sans fucking you in the middle of class. You really thought you had put it down in another document, but apparently, you’d written it out in your assignment. Luckily, you’d remembered to delete it. Well, most of it. All but that one damn line.

“continue,” Sans insisted.

You managed to look at him, and holy shit was that a mistake. You had thought he was looking at you salaciously before, but that was nothing compared to the absolutely pornographic way he was looking at you now.

“Out loud?” you asked, your voice barely more than a squeak.

He only nodded.

After a few seconds of silence, you finally began reading again. You skipped over that line. He knew you saw it. You knew he’d read it.

“you missed something.”

“I, um…” You were certain you would not be able to say those words out loud in front of the very person you fantasized about. “Professor…”

“is that really what you want?” he asked, his voice going low and soft. “is that why you’re taking an advanced class you don’t need for your degree?”

A click behind you made you jump. You turned quickly to see who was coming in to interrupt your fantasy-turned-reality, but the door remained shut.

“i just locked it,” he reassured.

Oh, right. Sans never used magic in the classroom, but he’d done a few things with it when you’d meet with him one on one.  You sighed in relief and nodded.

Your focus was right back on him as he stood up and walked around the desk, stopping right in front of you. It could have been just your imagination, but you could almost swear the bottom of his shirt was glowing softly, a more subdued hue than his usual blue magic.

“say the word and this ends right now,” he said softly, reaching out to lift your face with two fingers under your chin. You nearly shivered at the feel of cool bone against your skin. “but if you want this…well, i’m certainly interested.”

Your brain had a hard time keeping up. “You…you want me, too?” You met his eye lights, small pinpricks of lust in his sockets.

He nodded, his grin growing more debauched by the second. “have for a while. it’s all your fault, too, y’know. showing up at my office asking questions you already know the answers to. at first, i thought you were just curious about having a monster for a professor, but the more you came by the more i noticed certain…things.”

Sans took your hand and pulled gently, urging you to stand beside him. You did and swallowed as he lifted your hand and kissed the back of it.

“i’m pretty good at reading people, y’know.  especially when i catch you staring at me in class like you’re trying to rip my fucking clothes off with your eyes.”

You blushed hard and looked down at his shirt. “It’s not my fault you have a terrible sense of fashion.”

He laughed at that, then his fingers returned to your chin to get you to look at him. “we got an hour before i have to start class.”

You nodded and took a stabilizing breath before shoving forward and pressing your lips to his teeth.  He pulled you up so close to him that you could feel his arousal hard against your hip through his pants. You were pretty sure your brain short-circuited at that point. You felt yourself grind against the bulge as you whimpered against his mouth. In return, he moaned and let a hand slip down to your ass.

Well. If you were going to do this, you were going to fit in as many possible fantasies as you could. Who the fuck knew if this would happen again.

You slipped from his grasp only to sink to your knees. He swore under his breath as you reached for the waistband of his shorts.

“I’m not sure I can really tell you how long I’ve wanted to do this, Professor,” you said with a husky voice. “How many times I’ve thought about coming in here just to suck you off.”

“fuck…” His right hand was in your hair as you pulled his shorts down enough to free his cock.

You had been insanely curious about his dick for a long damn time, and you had come up with so many different ideas of what it could be made out of or how it might look. To have confirmation that it was actually made out of his pale blue magic and shaped like a regular, human-looking cock made your whole body begin to throb with desire.

You gave an experimental lick at the precum that had seeped from his tip. His answering gasp went straight to your cunt. You let your tongue swirl around his tip a few times before you spit on him and used it to make sliding your hand up and down his shaft easier.

You looked up at his face as you took him as far as you could. His eye lights morphed into hearts for a second before his sockets slid shut and he swore again, his hand in your hair gripping tightly.

A part of you wanted to continue going until he came in your mouth, but you really weren’t sure about that. You wanted this cock in your pussy, too. After a moment, you pulled back and stood up.

Sans kissed your deeply for a second before pulling back. “fucking hell, baby, i can’t wait to feel your sweet cunt. turn around for me.”

Just as you were, a knock on his office door stopped you both in your tracks.  You looked at him, eyes wide and terror gripping your gut. If you were caught, he could get fired.  He looked just as scared as you, but only for a quick second. It passed quickly, and before you had a chance to understand the new, devious grin on his face, he pulled you up close to him.

“hold on tight,” he whispered into your ear.

You did, pressing your body to his even though you knew being caught like this was the worst possible thing that could happen.

Then all of a sudden the world shifted around you. Blackness was everywhere for only a blink, then you were somewhere else.

You looked around, utterly confused. You were in a different room with a desk in the center and papers strewn about. It was the same sort of chaos as the office you’d just left.

“What…” You weren’t sure you could even ask a question at this point. You were too confused.

“sorry ‘bout that,” he said with a hand on the back of his cervical vertebrae. “had to get us out of there. this is my home office.”

Your brow furrowed. “We’re not at the university?” You looked around again, dumbly.

“nope.” He stepped toward you, pants still down and erection still hard. “you okay?”

Slowly, you began to realize what had actually happened. “You can teleport.” It wasn’t a question, although it probably should have been.

His smirk was adorable. “yeah.”

“That is the coolest thing I have ever experienced!”

His face turned a cute shade of blue. “it comes in handy sometimes.”  He reached out and touched your cheek. “you wanna stop?”

“Fuck no.” You gripped his dick, rubbing gently as you kissed him. “Is anyone else home?”

“nope. just us.”

“Then we can be as loud as we want, right?”

His hands began lifting up on your sweater. “absolutely.”

You let him undress you and guide you over to his desk where you sat on the edge. He sank to his knees before you and gave you a wink before he stuck out a tongue and licked your pussy.  You rested back on your elbows and moaned as he worked. His tongue flicked across your clit as he pushed a finger inside, and your stomach clenched as your right hand reached out to grip the back of his skull.

“Oh! Oh, _fuck_ , Sans!”

You expected him to stop when you neared your orgasm.  Instead, he curled his fingers and moved his tongue slowly and deliberately across your clit, causing you to cry out as you came hard enough to send a rush of arousal leaking down your thighs.

He pulled back then and made a show of licking his fingers clean. The fierce gleam in his eye lights and rock-hard cock only excited you; you’d never had a lover that cared so much about your pleasure. You’d be lucky to get one orgasm unless you were helping yourself.

“i want you to bend over,” he said, his voice low and rough. It sent another shock of arousal through your body.

“Yes, Professor,” you said with a sweet smile on your face.

Sans pulled you up and kissed you roughly before turning you around and all but shoving you down, bending you over the desk. Although a little surprised by his rough treatment, you couldn’t help but admit that it turned you on even more.

“i’m gonna make you cum again,” he growled out as you felt his tip against your pussy. 

He pushed in roughly, but there was no pain. Your whole body jerked as pleasure sparked through you. His hands on your back pushed you down onto the desk as he set a rough pace, fucking you hard enough to rattle the few trinkets he had set out. Your fingers gripped at the edge of the desk, grasping for something to hold onto as you cried out.

“fuck, Sans!” You felt his bones shiver behind you.

“that’s no way to address your fucking superior!” he slapped your ass, causing you to cry out helplessly.

“Professor…” you tried, your voice a whimper.

“that’s right.” He ground against you, his dick reaching all the right spots inside you. “say it again.”

“Goddammit, Professor, you fuck me so good!”

He leaned over you and pressed a kiss to your shoulder as one hand scratched lightly down your back.  “can’t tell you how long i’ve wanted this,” he confessed. His hand slipped under you, and you choked out a cry as he began rubbing your clit. “cum for me, sweetheart.”

You were so close. “Please, Professor…just a little more.”

He pounded into you harder and rubbed your clit more deliberately. His breathing was erratic as he swore against your skin before biting down and growling low in his chest.

“Faster,” you begged, so fucking close. 

Sans whimpered but gave you what you needed. He kissed your ear as he begged, whispering against the shell of your ear.

“i can’t hold back much longer, sweetheart. your cunt is too good. i wanna feel you cum before i do. please… _please_ , baby.”

Your body seized up as pleasure exploded throughout your being. Your back arched and your eyes clenched shut so tightly you saw stars as you came around his cock.  His movements stilled, his body pressed tightly to yours and his dick buried deep inside you as he came, choking out wordless cries against your hair.

You both slumped down on the desk for a few short minutes, panting heavily as you came down from the incredible high. He pulled out slowly, a mix of your own arousal and his cum dripping from you as he did. Sans kissed your shoulder one more time before he stood up.

“i’d ask if you wanna shower with me, but i got class in fifteen minutes. let me get something to clean you up with.”

Before you could respond, you were alone. You stood up and grimaced at the feel of more cum sliding down the inside of your thighs. You began to gather your clothes, setting them in a neat pile while you waited for Sans to come back.

He was only gone a few minutes. He returned with a pop of magic, a few rags in his hands. He’d already cleaned and redressed himself, it seemed.

Sans walked up to you and gave you a kiss before going back down on his knees. For a moment, you thought he might try to lick you again. It seemed that ‘insatiable’ was a good word for you at the moment. You were sadly disappointed when only cleaned you with the rag.

“that ought to do for a bit,” he said as he stood back up.

You nodded and kissed him once more before you got dressed. You noticed his eye lights on you and grinned as you made it as much of a show as getting dressed could be, pulling your panties up your thighs slowly and giving him a wink as they covered your ass.

You didn’t know where things stood between you and your professor. He’d go back to teaching and you’d be his student once more, at least until the end of the semester. You wanted to believe that this could happen again, but you sure didn’t want to risk getting him fired because you couldn’t keep your legs shut.

Neither of you spoke about it. Sans teleported you both back to his office at the university where he handed you the paper you’d turned and asked you to edit it once more before you turned it in for a final grade. You nodded, gave him one last kiss, and left. You really didn’t want to leave, but he had a class to teach.  You decided to go home and shower; you’d see him later tonight in class anyway.

* * *

 

**EPILOGUE**

Your phone chimed once again, and you quickly abandoned the idea to chuck it across the room. In your infinite wisdom, you’d posted your grades to Facebook along with expressing your excitement over having passed all of your finals with flying colors. It seemed every single person you knew or had friended on Facebook was texting or replying to your post to congratulate you.

That was fine and all, but now with the semester out of the way, you wanted to do something forbidden by college life and actually sleep in for once. That goddamn phone chiming every few minutes was not allowing you to do so.

Instead of throwing your phone, you picked it up to see who was texting this time.

You sat up when you saw the name. Professor Sans.

After your tryst with him a few weeks prior, you had both decided that it would be best to pretend it hadn’t happened until the semester was over. It would be so much easier than trying to hide a relationship that could get him into serious trouble, possibly even ruin his career.

As the days passed and communication between the two of you dwindled, you had come to fear that he wouldn’t be interested anymore. You weren’t going to give up, but something inside you warned you not to keep your hopes up.

You took a deep breath as you opened the message.

_hey. semester’s over…call me if you wanna get coffee sometime._

As you were typing a message back, another one came in.

_i mean real coffee. not asking for sex. unless you want that. uh. not good at this shit, sorry._

You snorted and continued typing your reply.

_Coffee sounds great. So does sex, to be honest, but I’m so exhausted from finals that I’m sure I’d be no fun._

It only took a few minutes before he sent a reply.

_lazy, sleepy sex is great sex and you cannot convince me otherwise. wanna meet for lunch tomorrow at that diner on second?_

You smiled brightly and typed back.

_That sounds great. Does noon work for you?_

You texted back and forth for a while, hashing out schedules and figuring out a time that worked for you both. Once your plan was set, you put your phone on silent and laid back down to hopefully get caught up on some sleep.

**Author's Note:**

> Most colleges here in the US have strict policies against any faculty pursuing a relationship with any student that they hold any sort of power over. Once that faculty member no longer holds power over the student, it's pretty much up to the individual college how they want to handle faculty/student relationships. Some strictly forbid it while others are cool with it even if they agree it's not a great idea. For this story, I'm going to pretend that the college in question is cool with faculty/student relationships as long as there's no power imbalance, hence why Sans and Reader are good to pursue their relationship once the semester is over and she's no longer his actual student.


End file.
